MISCELLANEOUS: EXPERIMENTAL TERATOSIS 579 



Either way from this stage the degree of susceptibility usually 

 falls rapidly. 



5. Internodes are most susceptible to shock when they are 

 about Me to % inch long, and leaves when the folded 2-stipule- 

 covered blades are about Y to ^ inch long, but responses can 

 be obtained from considerably larger leaves (blades \Y^ inches 

 long, or more). The closely wrapped terminal bud (Fig. 42SA) 

 usually contains three plainly visible young leaves, each sepa- 

 rately stipule-wrapped. The outermost is usually about % 

 inch long (Fig. 42SB, enlarged) including the petiole. The one 

 next above it is usually about ${$ inch long, while the third is 

 a mere red speck about He inch long. Above these three young 

 leaves are several undifferentiated colorless rudiments. 



6. I can now produce the response (teratosis) on a given 

 leaf or internode at will. That is to say, in the summer of 

 1918 I made experiments, predicted the results, and two months 

 later saw my predictions fulfilled to the letter, not once or 

 twice, or on a single plant, but in at least 150 places on 34 

 different plants. 



7. The response to the shock is in the form of great numbers 

 of adventitious embryo plants covering the surface of the leaves 

 and other shocked parts (Figs. 429, 430). Very often the num- 

 ber of sporadic plants growing out of a shocked leaf-blade has 

 been as many as 500 or 600 and occasionally they have ap- 

 peared in much greater numbers (2500 to 4000) the leaves above 

 and below (Figs. -430, 433, 440, 446) being free or nearly free 

 from shoots. The petioles, likewise, respond freely, some- 

 times bearing as many as 500 of these tiny plants (Figs. 429#, 

 436^1 x, 438, 4395, 443, 445?/). Also on single internodes re- 

 mote from leaf axils I have obtained from 200 to 2000 such 

 diminutive plants, the internodes above and below the shocked 

 ones being free or nearly free (see Figs. 429, 432, 434, 436, 437, 

 439A, 444, 445, 449 sub. 3, and Table II). 



8. Most of these crowded shoots perish after some weeks, 

 but a considerable number of them live for months, growing 



restricted to the main veins. Contrast with Figs. 441, 442 and 443. There are 

 no shoots on the lower surface. Photographed January 14, 1918. X 4. It was 

 appearances like this and those in Fig. 426 which led me to make these experiments. 



